Sealing system for a packaging machine

ABSTRACT

The following invention relates to a packaging machine with a sealing system comprising a front jaw and a rear jaw which reciprocate between an open-and a sealing-position, respectively, whereas a front jaw comprises two guide shafts which are supported in a frame.

The present invention relates to a packaging machine with a sealingsystem comprising a front jaw and a rear jaw which reciprocate betweenan open- and a sealing-position, respectively, whereas the front jawcomprises two guide shafts which are supported in a frame.

Such a packaging machine is known from the state of the art and is forexample a so called vertical flow wrapper in which a film is formed intoa tube and is provided with a longitudinal seal. This tube is filledwith the packaging item and a cross seal is provided at the lower andthe upper end of the package. Subsequently, the package is separatedfrom the film tube. The cross seal is applied by a sealing system whichcomprises a front jaw and a rear jaw which reciprocate between an openand a sealing position. The sealing system of these packaging machineis, however, rather complicated.

It was therefore the objective of the present invention to provide apackaging machine which does not comprise the deficiencies according tothe state of the art.

The problem is attained with a packaging machine with a sealing system,comprising a front jaw and a rear jaw, which reciprocates between anopen- and a sealing-position, respectively, whereas the front jawcomprises two guide shafts which are supported in a frame and whereasthe rear jaw is supported on the guide shafts of the front jaw.

The disclosure made regarding this embodiment of the present inventionalso applies to the other embodiments and vice versa.

The present invention relates to a packaging machine, which packages apackaging item into individual packages. Preferably this packagingmachine is a so called vertical flow wrapper, which forms a plain filminto a tube, provides a longitudinal seal to the film tube, fills thefilm tube with a packaging item and provides a cross seal at the top andat the bottom of each package in order to close the packagehermetically. Subsequently or simultaneously, the package is separatedfrom the film tube. In order to apply the cross seal to the package, theinventive packaging machine comprises a sealing system. This sealingsystem has a front jaw and a rear jaw, which reciprocate between anopen- and a sealing position. In the sealing position, the two jawsinteract and apply heat and/or pressure to the film tube in order toapply the cross-seal. In the open position, the two jaws are removedfrom the film tube. The front jaw comprises two guide shafts, which aresupported in a frame of the sealing system and which guide the linearmovement of the front jaw from its open to its sealing position and viceversa. According to the present invention, the guide shafts of the frontjaw are also utilize to support/guide the rear jaw during its linearmovement from the open- to the sealing-position and vice versa. Thisassures, that there is no offset between the front and the rear jaw andthat the system is very stiff.

According to another or a preferred embodiment of the present invention,each guide shaft of the front jaw comprises two bearings, respectively.According to this embodiment of the present invention, all these fourbearings are situated in a frame which is made from a single piece. Thisreduces manufacturing tolerances, simplifies the construction andprovides optimal stiffness.

The disclosure made regarding this embodiment of the present inventionalso applies to the other embodiments and vice versa.

According to a preferred embodiment of the present invention, onebearing of each guide shaft of the front jaw is located between thefront jaw and the rear jaw. This preferred embodiment of the presentinvention gives the sealing system maximum stability in the sealingposition, since, during sealing, the frame, the front jaw and the rearjaw are very close together.

According to another or a preferred embodiment of the present invention,the front jaw and the rear jaw are connected to a beam, respectively.Both these beams are, according to this embodiment of the presentinvention, supported at the frame by linear guiding means. This avoids,that the guide shaft of the front jaw are subjected to shear forces.

According to another or a preferred embodiment of the present invention,the motor drives the jaws and provides the pressure needed for thesealing with ultrasonic sound. There are no other means needed toposition the jaws and/or to provide the necessary pressure during theultrasonic sealing.

According to a preferred embodiment of the present invention, thebearings of the inventive packaging machine are free from play.Preferably, the play between the bearing and the bared part is less than20, preferably 10 micrometers.

Preferably, the jaws are driven by a servo motor.

According to another preferred embodiment of the present invention, theframe of the sealing system is made from two segments, which areconnected by two side plates.

Preferably, the connection between the two segments and/or theconnection between the side plates and the segments comprises dowelpins, in order to reduce manufacturing tolerances.

Preferably, at least one sealing jaw comprises a sonotrode for sealingof the film material with ultrasonic sound.

According to a preferred embodiment of the present invention, each jawcomprises two connections with shaft, respectively, whereas oneconnection of each jaw is preferably an adjustable connection and oneconnection of each jaw is preferably a fixed connection. This adjustmentallows the exact positioning of the jaws relative to each other,particularly the parallel positioning of the jaws in one or two planes.Additionally or exclusively, the jaws can be adjusted relative to theshaft at a certain temperature, respectively. Preferably, the connectionbetween the front jaw and the shaft comprises an adjustable bush in achamber in the front jaw. Preferably the connection between the rear jawand the shaft is an adjustable block. The jaws will be assembled andadjusted at a certain temperature.

Preferably, the sealing system comprises a heating- and/or cooling-meansand more preferably a temperature sensor. The sealing system canpreferably only be started and/or operated in case the temperature ofthe sealing system, particularly the temperature of one or both jaw(s)is/are in a range of the temperature at which it has been adjusted. Ifthe temperature is out of this range, one or both jaws will either becooled or heated. Preferably the rear jaw comprises an anvil which isheated to adjust the temperature.

Preferably, the sealing system comprises a film sensor. The sealingsystem can only be operated when the film sensor detects the presence ofa film.

Another subject matter of the present invention is a sealing-jaw of apackaging machine that comprises heating- and/or cooling means.

The disclosure made regarding this embodiment of the present inventionalso applies to the other embodiments and vice versa.

The heating and/or cooling means are utilized to heat or cool thesealing jaw to a certain temperature and/or to maintain the sealing jawat a certain temperature. Preferably, the heating means is an electricalheating means, for example one or more heating cartridge(s). Preferably,the heating- and/or the cooling means are designed such that anvil ofthe jaw and the bearings of the sealing jaw comprises an at leastessentially uniform temperature, respectively. This assures that thereis no or only minimal distortion in the anvil, the bearings and/or thejaw, so that so that the front jaw and the rear jaw are perfectlyparallel, which is particularly essential for the sealing of a thinfilm. The cooling means is preferably a tube system, preferably a tubecircuit, in which a liquid, preferably water flows and is preferablycirculated and which, more preferably is provided within the anvil ofthe sealing jaw. The water flow can be also utilized forheating-purposes. Preferably, the tube system extends along the front-and along the rear side of the anvil. This also assures an, at leastessentially, equal temperature of the anvil and thus no distortion.Preferably, a temperature sensor is provided at the anvil, in thevicinity of the anvil and/or in the liquid to measure the temperature ofthe anvil. Preferably, the temperature of the liquid that is passedthrough the anvil is 45-50° C., more preferably 48-52° C.

The heating means are preferably utilized to bring and/or maintain therear jaw at a certain, more preferably a minimum, temperature.

Another subject matter of the present invention is a method to seal apackaging with two jaws, whereas at least one jaw, preferably the rearjaw, is tempered prior to sealing.

The disclosure made regarding this embodiment of the present inventionalso applies to the other embodiments and vice versa.

This embodiment of the present invention assures that the quality of thesealing of the film is acceptable even during the entire productionperiod, even after start-up at the beginning of a shift. The temperatureof the jaw, particularly the rear jaw and preferably, at least the anvilis heated until a certain temperature is reached. Only then, theinventive packaging machine starts its production. The heating ispreferably executed by one or more electrical heating means, preferablyheating cartridge(s).

Yet another subject matter of the present invention is a method to seala packaging with a sonotrode, whereas the sealing period is adjustedbased on the temperature of the sonotrode. According to the presentinvention, a package, made from a plastic film is formed, filled with apackaging item and then hermetically closed by sealing the film. Thesonotrode is untilized to seal a film with ultrasonic sound. Thesonotrode provides the ultrasonic sound.

The disclosure made regarding this embodiment of the present inventionalso applies to the other embodiments and vice versa.

According to the present invention, the sealing time is adjusted basedon the temperature of the sonotrode. Preferably, the sealing time isdecreased with increasing temperature of the sonotrode. The sealing timeis the time during which the two sealing jaws are pressed together.

Preferably, the inventive packaging machine and/or the inventive methodis self adapting. For example, after a certain time period after thestart of the packaging machine and/or after a certain amount seals havebeen applied to the film, a control system automatically reduces thesealing time. Alternatively, the temperature of the sonotrode isdetermined and based on this reading, the sealing time is automaticallyadjusted.

The inventions are now explained according to FIGS. 1-9. Theseexplanations do not limit the scope of protection. The explanationapplies to all inventions, respectively.

FIG. 1 shows the sealing system.

FIG. 2 shows the bearing of the guide shaft.

FIG. 3 shows the linear guiding means.

FIG. 4 shows the connection between the frame and the side plates.

FIG. 5 shows the bearings in the frame.

FIG. 6 shows the sealing system.

FIG. 7 shows the connection between the jaws 2, 3 and the guide shaft.

FIG. 8 shows a film sensor.

FIG. 9 shows the inventive sealing jaw

FIGS. 1 and 6 show the sealing system 1 of the inventive packagingmachine. This sealing system 1 comprises a front jaw 2 and a rear jaw 3which reciprocate between an open- and a sealing-position. The sealingposition is depicted in FIG. 1 and the open position is depicted in FIG.6. The front jaw 2 is connected to two guide shafts 4, which aresupported in a frame 13 of the sealing system 1. At their rear end, theguide shafts 4 are connected to a beam 5. As can be particularly seenfrom FIG. 6, the rear jaw 3 comprises bearings 22, which support therear jaw 3 at the guide shafts 4 of the front jaw 2. Each bearing 22comprises preferably two segments, which are separated from each otherso that a moment of a torque can be easily transferred from the rear jaw3 to the guide shaft 4. Additionally, the rear jaw 3 is connected to twodrive shafts 7, which comprise at their rear end a beam 6. Each beam 5,6 is connected with one end of a crank 8, respectively. The other end ofthe cranks 8 are connected to a rotational drive 9, which is driven by amotor 17, preferably a servo motor. By turning the rotational driveclockwise, the front jaw 2 and the rear jaw 3 move from their openposition to the sealing position. A counter clockwise rotation of therotation drive 9 results in a movement of the jaws 2, 3 into their openposition. In order to avoid, that the guide shaft 4 and/or the driveshaft 7 is subjected to a shear force, both beams 5, 6 comprise abearing 18, respectively, each supported on a linear guiding means 19.As can be also seen from FIG. 6, two bearings 15 of the guide shaft 4are located between the front shaft 2 and the rear shaft 3. Thisassures, that the bearing and the front and the rear jaw 2, 3 are inclose proximity during sealing. As can be also seen from FIG. 6, eachguide shaft 4 is supported by two bearings 15, 16, respectively, whichare relatively far apart in order to increase the stiffness of thesystem. All four bearings 15, 16 are situated in a first segment 13.1 offrame 13, which is machined from a single piece of metal. The entireframe 13 is, in the present case, made from two segments 13.1, 13.2,which are connected to each other by two side plates 14. One segment,13.1 comprises all four bearings 15, 16, the other segment 13.2comprises the beam 5, 6 for the jaws 2, 3. In order to reducemanufacturing tolerances, the segment 13.1, 13.2 and all the side platesare connected to each other by dowel pins 20 which can be particularlyseen from FIG. 4. All bearings 15, 16, 22 are preferably play freebearings, for example ball recirculating sleeve bearings. In the presentcase, the sealing of the film, particularly the cross-seal is providedby means of a ultrasonic sound. Therefore, the sealing system comprisesa sonotrode 28, in the present case two sonotrodes 28, which areoperated in parallel and which are both connected to the front jaw 2.Preferably, the position of both sonotrodes 28 relative to the front jaw2 can be adjusted individually. Preferably, the frequency and/or theamplitude of each sonotrode can be set individually.

Reference is now made to FIG. 2. It can be clearly seen, that each shaft4 is supported to the frame 13 by bearings 15, 16, which are separatedfrom each other. All four bearings 15, 16 are supported in one segment13.1 of frame 13, which is manufactured from a single piece of metal.

In FIG. 3, the linear guiding means 19 of the beams 5, 6 can be seen,each beam 5, 6 comprises a bearing 18, in the present case a play freebearing, which is supported on the linear guiding means 19. Thecooperation of bearings 18 and the linear guiding means 19 avoid, thatshear forces are introduced into shafts 4 or shafts 7. Preferably, thebearing is a ball recirculating sleeve bearing.

FIG. 4 shows the connection between the segment 13.1 and side plates 14.The connection comprises dowel pins 10 and fastening means here screws21. The dowel pins assure the exact positioning between the segment 13.1and the side plate 14.

From FIG. 5, it can be seen, that all four bearings 15, 16 are situatedin one segment 13.1 of frame 13.

According to FIG. 7, each jaw 2, 3 comprises two connections 22.1, 22.2,23.1, 23.2 with the shafts 4, respectively, whereas one connection 22.1,23.1 of each jaw 2, 3 is an adjustable connection and one connection22.2, 23.2 of each jaw 2, 3 is preferably a fixed connection. Thisadjustment preferably allows the exact positioning of the jaws 2, 3relative to each other, particularly the parallel positioning of thejaws 2, 3 relative to each other in one or more plane(s). Additionallyor exclusively, the jaws 2, 3 can be adjusted relative to the shaft 4 ata certain temperature, respectively. Preferably, the connection betweenthe front jaw and the shaft comprises an adjustable bush in a chamber inthe front jaw. Preferably the connection between the rear jaw and theshaft is an adjustable block. The jaws will be assembled and adjusted ata certain temperature. Preferably, the sealing system comprises aheating- and/or cooling-means and more preferably a temperature sensor.The sealing system can preferably only be started and/or operated incase the temperature of the sealing system, particularly the temperatureof one or both jaw(s) is in a range of the temperature at which it hasbeen adjusted. If the temperature is out of this range, one or both jawswill either be cooled or heated or the system will be shut down.Preferably the rear jaw comprises an anvil which is heated to adjust thetemperature.

In FIG. 8, the sealing system comprises a film sensor 24. The sealingsystem can only be operated when the film sensor 24 detects the presenceof a film.

FIG. 9 shows the inventive rear sealing jaw 3, which comprises, in thepresent case, an anvil 27 and two bearings 22.1, 22.2, in the presentcase designed as bearing-blocks. In the present example, the sealing ofthe film is applied by ultrasonic sound, which is provided by asonotrode, which Is part of the front jaw 2. At its front side, theanvil comprises a sealing bar 29, which is in contact with the film, inorder to apply the seal to the film, which, during sealing, is pressedbetween the sonotrode 28 and the sealing bar 29.

According to the present invention, the rear jaw 3, particularly itsanvil 26 is heated and/or cooled, to bring and/or maintain the sealingjaw and/or the anvil at a certain temperature, whereas a uniformtemperature, particularly over the entire anvil 26. A uniformtemperature distribution over the anvil 26 assures that no or onlylittle distortion of the anvil takes place, so that the sealing bar 29is always parallel to the sonotrode. In the present case, the heating iscarried out by two cartridges 25. The cartridges are particularlyutilized to increase the temperature of the rear jaw after a longerproduction-break. Additionally or alternatively, the anvil comprises atube system 26 in the anvil 27. Through the tube system, a liquid,preferably water, is passes to cool and/or heat the rear jaw. The tubesystem can be part of a closed loop comprising a heat-exchange-elementto heat or cool the temperature of the liquid, if needed. As can beclearly seen, that the tube system extends along the front end 26.2 andalong the rear end 26.1 of the anvil, in order to achieve a uniformtemperature in the anvil. The person skilled in the art understands,that heat can be transferred from the anvil to the bearings in order toadjust, i.e. heat and/or cool, their temperature. Preferably the anviland the bearings are at the same temperature.

Before the operation of the inventive packaging machine is started, forexample at the beginning of morning shift, the rear jaw is preferablyheated to its operation temperature. This is preferably done by theelectrical heating elements 25. As soon as this temperature has beenreached, the packaging machine starts packaging articles.

LIST OF REFERENCE SIGNS

-   1 Sealing System-   2 Front jaw-   3 Rear jaw-   4 Guide shaft, drive shaft-   5 Beam for the front jaw-   6 Beam for the rear jaw-   7 Drive shaft rear jaw-   8 Crank-   9 Rotation means-   10 Linear guide-   11 Bearing for the vertical movement of the system-   12 Bearing for the rear jaw-   13 Frame-   13.1 first segment of the frame-   13.2 second segment of the frame-   14 Side plate-   15 Bearing for the guide shaft 4-   16 Bearing for the guide shaft 4-   17 Motor-   18 Bearing-   19 Linear guiding means-   20 Dowel pin-   21 Fastening means, screw-   22 Bearing of the rear jaw-   23 Connection between the front jaw and the guide shaft-   24 Film sensor-   25 heating cartridge-   26 liquid circuit-   27 anvil-   28 sonotrode-   29 sealing bar

1. A packaging machine with a sealing system comprising: a front jaw anda rear jaw, which reciprocate between an open- and a sealing-position,respectively, whereas the front jaw comprises: two guide shafts whichare supported in a frame, wherein the rear jaw is supported on the guideshafts of the front jaw; a sonotrode for sealing the film material withultrasonic sound; wherein a motor drives the jaws and provides thepressure needed for the sealing with ultrasonic sound; and wherein thefront jaw and the rear jaw comprise heating- and cooling means.
 2. Thepackaging machine according to claim 1, wherein each of the two guideshafts comprises two bearings, respectively and that the two bearingsare situated in a frame which is made from one single piece.
 3. Thepackaging machine according to claim 1, wherein a bearing of the guideshaft is located between the front jaw and the rear jaw.
 4. Thepackaging machine according to claim 1, wherein the front jaw is coupledto a beam and the rear jaw is connected to a beam and that each beam issupported at the frame by a linear guiding means respectively. 5.(canceled)
 6. The packaging machine according to claim 1, wherein thebearings are free from play.
 7. The packaging machine according to claim1, wherein the front jaw and the rear jaw are driven by a servo motor.8. The packaging machine according to claim 1, wherein the frame is madefrom two pieces which are connected by two side plates.
 9. The packagingmachine according to claim 8, wherein the two pieces of the frame and/orthe side plates are connected by dowel pins.
 10. (canceled)
 11. Thepackaging machine according to claim 1, wherein each of the front jawand the rear jaw comprises two connections with shaft, respectively,whereas one connection of each jaw is an adjustable connection and oneconnection of each jaw is a fixed connection.
 12. A sealing-jaw of apackaging machine for sealing of a film with ultrasonic sound, whereinthe sealing-jaw comprises heating- and/or cooling means that maintainthe sealing jaw at a uniform temperature, wherein the heating means areelectrical heating means and the cooling means is a tube system throughwhich a liquid flows.
 13. The sealing-jaw according to claim 12, whereinthe sealing-jaw comprises an anvil and that the heating- and/or coolingmeans are distributed at the front- and at the rear part of the anvil.14. Method to seal a packaging with two jaws, wherein at least one jawis tempered prior to sealing, or with a sonotrode, wherein a sealingperiod is adjusted based on a temperature of the sonotrode. 15.(canceled)
 16. The packaging machine according to claim 2, wherein abearing of the guide shaft is located between the front jaw and the rearjaw.
 17. The packaging machine according to claim 2, wherein the frontjaw is coupled to a beam and the rear jaw is connected to a beam andthat each beam is supported at the frame by a linear guiding meansrespectively.
 18. The packaging machine according to claim 16, whereinthe front jaw is coupled to a beam and the rear jaw is connected to abeam and that each beam is supported at the frame by a linear guidingmeans respectively.
 19. The packaging machine according to claim 2,wherein the front jaw is coupled to a beam and the rear jaw is connectedto a beam and that each beam is supported at the frame by a linearguiding means respectively.
 20. The packaging machine according to claim18, wherein the front jaw is coupled to a beam and the rear jaw isconnected to a beam and that each beam is supported at the frame by alinear guiding means respectively.
 21. The packaging machine accordingto claim 20, wherein the bearings are free from play.
 22. The packagingmachine according to claim 21, wherein the front jaw and the rear jaware driven by a servo motor.
 23. The packaging machine according toclaim 22, wherein the frame is made from two pieces which are connectedby two side plates.